If the line inet6 addr: fe80::290:4bff:9999:0000 /64 Scope:Link is missing, your system does not have ipv6 support. You may need to explicitely make webcit bind ipv4 then by specifying -i 0.0.0.0; else you may get the error message 'Address family not supported by protocol'.

If you prefer to see the names of the services than their port numbers you can omit the -n

If you have chosen to let your citserver bind a secific IP, the whole thing will look a little different.
Lets say, your machine has the ips 127.0.0.1(loopback) 1.1.1.1 and 1.1.1.55, and you want citadel just to answer queries on 1.1.1.55 since other services are already answering on the above listed ports on 1.1.1.1 the lines will look like that:

Telnet is an unencrypted remote terminal tool. But we can also abuse it to check whether citadel is able to do its job:

by talking to localhost (127.0.0.1) from a shell on the host your citserver runs on to check its actually citadel you're talking to

if you replace 127.0.0.1 by i.e. smtp1.google.com check whether your Citadel server is able to send mail out; the replies will look a little different then.

also you can use it to check whether the outside world is able to reach you. Use some outside Internet connection such as a mobile or an internet cafe to your Citadel server, or ask someone outside of your network to do this for you.

We have illustrated the conversation with - > and < - to show what you type, and what the mail server (in this case a Citadel) sends back.

You could make Citadel receive or send out an email this way. Furthermore, you have now confirmed that you are talking with the Citadel SMTP service, not with another email program left over from a previous or default installation.
The reply to the EHLO command also shows you which kind of authentication the host supports (another sample would be CRAMD-MD5). Citadel itself just supports “plain” auth, in receiving and sending direction. This is almost plaintext, so you should wrap a TLS session around it.
If you don't see

220 yourserver ESMTP Citadel server ready.

but something like Postfix, Exim, QMail you are not talking to your Citadel server.

Note: depending on your system netcat may either be named nc or netcat; we'll name it nc in the examples.
Netcat was designed for the purpose for which we misused telnet earlier. If you want for example to post a message using an automated script, telnet would add special control characters, which will spoil your effort. You need to use netcat in this case. But netcat can do even more: It can open server sockets (like citserver does) or speak UDP.

The problem we want to use netcat for in this example is the following: You want to know which headers your browser sends to webcit.
For that we need netcat to open a server socket, our browser will talk to:

Here we want to use netcat to talk to your citserver in citadels native tongue; this is usualy done through TCP Port 504 (see your output of netcat above); (we'll add » and « for whats Citserver telling you, and what we tell him; You'll get similar output if you configure and compile webcit with CFLAGS += -D SERV_TRACE)

Now if you want to do this from within a shellscript, you'll get the problem that NetCat will close the connection to the server when its input channel is closed; ence we need to make it waiting; we'll use '()' (which invokes a sub-shell) for that:

To resolve IP addresses from names like google.com, your computer needs nameservers; the file /etc/hosts shows your programs where to find it. Verify that thie file exists, and that the IP address inside is reachable with ping.
Next you can use the nslookup or host utility to check if it's working: